The term cities may immediately conjure up soaring skyscrapers and bustling streets, but they come in plenty of other forms as well. This book, part of the Hidden, Lost, and Discovered series (4 titles), takes readers around the world to investigate various “underground” cities, from the familiar (elegant, stone-carved Petra) to the slightly more obscure (RÉSO, the vast series of tunnels designed to keep Montreal residents out of the cold). Stunning scenic photos establish the varied settings, including Turkey and China, with following shots focused on details and inhabitants. Each section incorporates a location map, occasional vocabulary help, tidbits of trivia, and a brief introduction to each city’s history and function, and back matter includes suggested comprehension questions and follow-up activities. Curious young readers will find this an appealing introduction to an intriguing subject.